Leber's congenital amaurosis (LCA) is the most severe form of inherited retinal dystrophy, with an onset of disease symptoms in the first years of life (Leber, T., Archiv fûr Ophthalmologie (in German). 15 (3): 1-25, 1869) and an estimated prevalence of approximately 1 in 50,000 worldwide (Koenekoop et al., Clin Experiment Ophthalmol. 35(5): 473-485, 2007; Stone, Am J Ophthalmol. 144(6): 791-811, 2007). Genetically, LCA is a heterogeneous disease. To date, fifteen genes have been identified with mutations that result in LCA (den Hollander et al., Prog Retin Eye Res. 27(4): 391-419, 2008; Estrada-Cuzcano et al., Invest Ophthalmol Vis Sci. 52(2): 834-9, 2011). The CEP290 gene is the most frequently mutated LCA gene accounting for approximately 15% of all cases (Stone, Am J Ophthalmol. 144(6): 791-811, 2007; den Hollander et al., Prog Retin Eye Res. 27(4): 391-419, 2008; den Hollander et al., Am J Hum Genet. 79(3): 556-561, 2006; Perrault et al., Hum Mutat. 28(4):4 16, 2007). Severe mutations in CEP290 have also been reported to cause systemic diseases that are characterized by brain defects, kidney malformations, polydactyly and/or obesity (Baal et al., Am J Hum Genet. 81, 170-179, 2007; den Hollander et al., Prog Retin Eye Res. 27(4): 391-419, 2008; Helou et al., J Med Genet. 44: 657-663, 2007; Valente et al., Nat Genet. 38: 623-625, 2006). Patients with LCA and early-onset retinal dystrophy often carry hypomorphic CEP290 alleles (Stone, Am J Ophthalmol. 144(6): 791-811, 2007; den Hollander et al., Am J Hum Genet. 79(3): 556-561, 2006; Perrault et al., Hum Mutat. 28(4):4 16, 2007; Coppieters et al., Hum Mutat 31, E1709-E1766. 2010; Littink et al., Invest Ophthalmol Vis Sci 51, 3646-3652, 2010).
LCA, and other retinal dystrophies such as Retinitis Pigmentosa (RP), have long been considered incurable diseases. However, the first phase I/II clinical trials using gene augmentation therapy have led to promising results in a selected group of adult LCA/RP patients with mutations in the RPE65 gene (Bainbridge et al., N Engl J Med. 358, 2231-2239, 2008; Cideciyan et al., Proc Natl Acad Sci USA. 105, 15112-15117, 2008; Hauswirth et al., N Engl J Med. 358, 2240-2248, 2008; Maguire et al., N Engl J Med. 358: 2240-2248, 2008). Unilateral subretinal injections of adeno-associated virus particles carrying constructs encoding the wild-type RPE65 cDNA were shown to be safe and moderately effective in some patients, without causing any adverse effects. In a follow-up study including adults and children, visual improvements were more sustained, especially in the children all of whom gained ambulatory vision (Maguire et al., Lancet. 374, 1597-1605, 2009). Although these studies demonstrated the potential to treat LCA using gene augmentation therapy and increased the development of therapeutic strategies for other genetic subtypes of retinal dystrophies (den Hollander et al., J Clin Invest 120: 3042-3053, 2010), it is hard to control the expression levels of the therapeutic genes when using gene augmentation therapy.
Leber's congenital amaurosis 10 (LCA10), one type of LCA, is is an inherited (autosomal recessive) retinal degenerative disease characterized by severe loss of vision at birth. All subjects having LCA10 have had at least one c.2991+1655A to G (adenine to guanine) mutation in the CEP290 gene. Heterozygous nonsense, frameshift, and splice-site mutations have been identified on the remaining allele. A c.2991+1655A to G mutation in the CEP290 gene give rise to a cryptic splice donor cite in intron 26 which results in the inclusion of an aberrant exon of 128 bp in the mutant CEP290 mRNA, and inserts a premature stop codon (P.C998X). The sequence of the cryptic exon contains part of an Alu repeat. There are currently no approved therapeutics for LCA10.
Despite advances that have been made using gene therapy, there remains a need for therapeutics to treat retinal dystrophies, including LCA10.